This invention relates to burst signal transmission, in a satellite communication network having a plurality of satellites orbiting the earth, between a great number of earth stations which may be fixed stations and/or selectively called mobile stations. In recent practice, the orbiting satellites are often called low earth orbit satellites. More particularly, this invention relates to a method of transmitting a burst signal from an arbitrary one of the earth stations to one of the orbiting satellites, to a burst signal transmitter device for use in such an earth station, and to a transponder for use on each orbiting satellite.
Satellites in geostationary orbit are in general use multiple access communication networks. Such a communication network was proposed circa 1950.
Large scale rockets have recently become available for launching small sized satellites accompanying a large sized satellite. Rockets have also been developed for launching small sized satellites. This has made it economical to launch small sized satellites. As a consequence, attention has been drawn to satellite communication networks employing a plurality of small sized orbiting satellites at low and/or middle orbit altitudes. Such satellite communication networks are superior to network using geostationary satellites because they allow shorter propagations delays between earth stations and compact transmission and reception terminals. As a typical example of communication networks using orbiting satellites, the IRIDIUM system of Motorola, Inc., U.S.A., is described in a report in the Japanese language in the periodical "Nikkei Kommunikeisyon" (Nikkei Communications), No. 112, published by Nikkei BP on the 21st of Oct. 1991, pages 31 to 32. This report is based on a paper entitled "Application of Motorola Satellite Communications, Inc., for a Low Earth Orbit Mobile Satellite System before the Federal Communications Commission, Washington, D.C., December 1990", of which eight pages are available to us, including the title page and two figure pages 1a and 1b.
As be described below in greater detail, it has been unavoidable to use a long guard time in a conventional burst signal transmitter of an earth station of such an orbiting satellite communication network the transmitting burst signals to other earth stations through one of orbiting satellites. The long guard time results in a reduced transmission efficiency.